Ampicillin is an aminopenicillin antibiotic that has been heavily utilized to treat a wide variety of bacterial infections since it first entered the pharmaceuticals market in the early 1960s. The semisynthetic substance is formed via the attachment of acid radicals to the basic structure of 6-aminopenicillanic acid.

The chief advantage of ampicillin over other types of penicillin is the relative stability of the substance in the stomach. Due to this important characteristic, the antibiotic may be administered orally, usually as a capsule, liquid, or pediatric drop. The ease with which this may be done has resulted in the drug’s immense popularity, it finding use in the treatment of a number of respiratory and urinary-tract infections, as well as bacterial meningitis, typhoid fever, and similar illnesses. Unfortunately, the heavy use of ampicillin is decreasing its effectiveness against some strains of certain infections, and, therefore, the drug must now often be utilized in combination with other pharmaceuticals.

Ampicillin is marketed under a variety of trade names, such as D-Amp, Omnipen, Principen, and Totacillin. Though rare, several side effects may occur from the utilization of these products. The most common of these effects include skin rash and hives caused by an allergic reaction to ampicillin. Anaphylactic shock may also result, but only in cases where the allergy is extremely severe. Other possible side effects that occasionally arise are stomach upset, vomiting, and diarrhea.